High Wavenumber Coherent Structures in Low Re APG-Boundary-Layer Transition Flow—A Numerical StudyReport as inadecuate


High Wavenumber Coherent Structures in Low Re APG-Boundary-Layer Transition Flow—A Numerical Study


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School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798, Singapore





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Academic Editor: William Layton

Abstract This paper presents a numerical study of high wavenumber coherent structure evolution in boundary layer transition flow using recently-developed high order Combined compact difference schemes with non-uniform grids in the wall-normal direction for efficient simulation of such flows. The study focuses on a simulation of an Adverse-Pressure-Gradient APG boundary layer transition induced by broadband disturbance corresponding to the experiment of Borodulin et al. Journal of Turbulence, 2006, 7, pp. 1–30. The results support the experimental observation that although the coherent structures seen during transition to turbulence have asymmetric shapes and occur in a random pattern, their local evolutional behaviors are quite similar. Further calculated local wavelet spectra of these coherent structures are also very similar. The wavelet spectrum of the streamwise disturbance velocity demonstrates high wavenumber clusters at the tip and the rear parts of the Λ-vortex. Both parts are imbedded at the primary Λ-vortex stage and spatially coincide with the spike region and high shear layer. The tip part is associated with the later first ring-like vortex, while the rear part with the remainder of the Λ-vortex. These observations help to shed light on the generation of turbulence, which is dominated by high wavenumber coherent structures. View Full-Text

Keywords: combined compact difference; numerical simulation; boundary layer transition; coherent structures; vortex dynamics; wavelet analysis combined compact difference; numerical simulation; boundary layer transition; coherent structures; vortex dynamics; wavelet analysis





Author: Weijia Chen and Edmond Y. Lo *

Source: http://mdpi.com/



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